Hydraulic control devices for intermittent displacements



Oct. 23, 1956 P. PEGARD 2,767,547

HYDRAULIC coNTRoL DEVICES FOR INTERMITTENT nIsPLAcEMENTs Filed March s, 195:5 5 sheets-sheet 2 Fig. 3

*All 42 l' 4a I T l 35 l 32 Oct. 23, 1956 P. PEGARD 2,767,547

HYDRAULIC CONTROL DEVICES FOR INTERMITTENT DISPLACEMENTS Filed March 9, 1953 3 Sheets-Sheet 3 2,767,547 Patented Oct. 23, 1956 Y 2,767,547 HYDRAULIC CONTRL DEVICES FOR INTER- 4 MITTENT DHSPLACEMENTS l Pierre Pgard, Courbevoie, France, assignor to Socit Anonyme dite: Ateliers G. S. P.Gu'i llemin-Sergot Pegard, Courbevoie, France, a society of France Application. March 9, 1953, Serial No. 341,260 Claims priority, application France December 31, 1952 Claims. (Cl. 60-52) The present invention has for its object a 4hydraulic control device enabling intermittent displacements to be imparted to a movable member.

(This device is susceptible of receiving numerous applications, but `it is more particularly suitable for machinetools, for example for producing `an intermittent feed motion.

=This device comprises a transmitter unit and a receiving unit which may be placed at a certain distance from each other and may be connected by means of fa flexible piping so that one or the other unit may 'be movable.

The receiving member receives a reciprocating movement which can be transformed into an intermittent feed Ithrough the intermediary of a device comprising a free wheel.

The amplitude` of the movement of the receivingy member may be variedY at will, and consequently that of the movable member may also be varied, even during operation and while in motion. Moreover, the receiving unit comprises an arrangement for hydraulic braking having yfor its purpose to gradually "brake at the end of their displacement the receiving members driven by the hydraulic pressure, to avoid the effect of the jar at the end of the run and consequently to damp the throw of the movable members comprised between the piston of the receiving unit andV its free wheel.

The throw of the receivingmembers beingdamped, it is permissible to obtain a practically constant value for the displacement of the table foreach hydraulic impulse, whatever may be the frequency of the strokes of the piston of the transmitter unit and consequently whatever may be the speed of the injection, thethrow of the controlled members comprised between the free wheel and the table being totally negligible.

The appended Adrawings represent, by way of example which is non-limitative, the application of the invention to the control of a table of a machine-tool.

`In these dnawings:

Fig. l yis ra sectional view of the entire device.

Fig. 2 is a corresponding partial side view.

Fig. 3 is a corresponding partial plan view.

`Fig. 4 is a section of Ithe motor unit and. of the receiving unit showing an alternative embodiment.

fFig. 5 is a section of the device shown in Fig `4 along As seen inthese drawings, the device according to the invention comprises a transmitter assembly M |and a receiving assembly R one of which may be placed at a `certain distance from the `other and which are .connected Eby a flexible piping C. These assemblies can therefore be carried by moving members.

The transmitter assembly (Fig. l) comprises a trough 1 in which :are placed the different parts and which constitutes an oil reserve. This trough .is also provided with a lid 2. The inside constitutes a block 3 forming the body of the cylinder for several pistons. One of the pistons is a plunger 4 which is pushed by a spring 5 and which is subjected to the action of a driving cam 6 through the intermediary of a rocking lever 7. This cam is keyed on a driving shaft 8 which is rotating continuously. Another cam 9 is keyed on the `same shaft and is' capable of acting by means of a leverl 10 on a rares Patent Ofice 2. closure piston 11 provided at its base with a small bent passage 12. 11n .line with the piston 11 is situated a differential piston 13 14, subjected to the` action of |a spring A15. Finally, |a `third sliding member comprising a piston having three lands y16, 17 and 1:8 constitutes a working and stopping valve. This valve is controlled by means of a rack 19 the end of which is cut out, with which meshes a pinion `20 aiXed to or integral with a controlling lever 21.

The receiving assembly comprises a hollow piston 22, mobile upon a tubular guide 23 and in which opens the piping C. This pistonV is subjected to the action of a return spring '24. Opposite the piston is a stop 25. The latter is adjustable and screws into a iiXed nut 26. The stop 25 is rotative'ly driven by a rod 27 aixed to or integral with a controllingknob :28. On this .rod is keyed a pinion 29, engaging a crown with internal teeth 30 on `whichis Xed a graduated disc 46.

In the case when the receiving unit controls the intermittent feed motion of a table T, the movement of displacement of the receiving piston 22 is transmitted 'by a rackj32 with which it is provided to `a pinion 33 afxed to or integral with the upper portion of a free wheel 34. The internal port-ion. is in4 one piece with a bevel pinion 35 in` engagement with two bevel pinions 36 and B7. The latter are aixed to orintegrlal with toothed wheels 38 and 39 turning freely onV a shaft di?. A sliding clutch 41, rotating in one piece with a shaft, 42 may be put in engagementy with one or the other of the wheels 38, 139. The shaft '42 is aixed to or integral. with a screw 43 adapted to screw into al nut 44 solid with the table T.

The operation .is asV follows:

At each turn ofthe shaft 8, the cam 6 pushes down the plunger fi while compressing they .spring 5.

'Let it be supposed that the lever 21 is in operating position, whichis that which is represented.

The oil, put under pressure by the pumpl piston 4, passes along the pipes b, a',k g, the flexible piping C and the pipe p, and lifts the piston 22 while compressing the spring 24. The Isaid piston advances until it is stopped by the stop 2S. ln the course of this movement, itcauses the pinion 33 to turn |and thisk pinion, through the intermediary of the free wheel 34, of the pinion 35 and of one or `the other of thepinions 38, 39, accordi-ng to the position of the sliding clutch y141, Fig. 3, drives the `shaft 42.. The screw screws itself in the nut 144 and displaces the table T. The direction of motion depends on the position of the sliding clutch 41.

At the moment when the piston 22 meets its stop, the pump piston 4 has not terminated its run and continues to descend. An excess of pressure accordingly takes place, owing to which the diferential piston 13-14 is lifted and pushes upwardsk the closure piston 11 which has been freed by the rotation of the cam 9. When the bottomof this piston uncovers the passage a, there is an opening to exhaust through a, and the passages 12, c and e. The passage 12 is not blocked against flow by the upper side of piston 13 because this latter piston is pulled downwardly by the spring 15 after it has raised the upper portion. The' differential piston descends again, but the closure piston remains lifted because the passage 12v is sufficiently narrow for a suilicient pressure to exist at a to maintain the closure piston in its raisedposition.

I Owing to the fall of pressure, the piston 22 is brought back upon its seat by the spring 24. This movement is transmitted to the part 34, but, in this direction, the pinion 35 is not rotated by the free wheel, so that the table T remains motionless.

When the piston 4 has terminated its descending course, it begins to rise again under the action of the spring-5, which presses it against the lever 7 in contact with the cam 6. This rise producesva fall of pressure. The ball 45 lifts and allows oil to re-enter through the passages k, i and The piston 4 terminates its ascending course, then the cam 6 compels it to descend again. The downward movement by the piston 11 had preliminarily taken place through the action of the cam 9. The` cycle begins again. It is therefore seen that, at each descent of the piston the table T effects a feed movement.

The amplitude of the feed is determined by the adjustment of the stop 2S, obtained by operating the knob 28. The stroke of the piston 22 can vary from 0 up to a maximum, in passing through all the -intermediate values. The adjustment is continuous. The amplitude of the movements of the table varies in a corresponding manner. The `feed given to the table is read on the graduation carried by the disc 46.

When the lever 21 is lowered, in the position shown in broken lines in Fig. l, the valve 16 is lifted and the passage d is put in Comunication with f. The pump piston 4 then moves without producing any effect. It is the position of rest for the receiving mechanism.

In the arrangement shown in Fig. 4, the receiving group R is similar to that of Fig. l, but it compr1ses in addition a piston 53 disposed so as to be parallel to the receiving piston 22. This piston 53 is provided laterally with a rack which isin engagement with the pinion 33 actuated by the piston 22. it can slide without play in a cylinder 54 and is provided at its end with a coical passage 56.` ,A ball 57 allows this cylinder to be rapidly filled with the oil contained in a container 55.

The transmitter assembly M shows, with respect to the arrangement shown in Fig. l, some modifications of detail having for their object to simplify the apparatus.

The cam 6 actuates directly the transmitter piston 4.`

The hydraulic injection is direct in the flexible piping C which is extended from a rigid pipe 58.

A discharge check-valve 45, adjusted by a spring 48 and a screw 47, enables the excess of the driving liquid to escape as soon as the stroke of the receiving piston 22 has been adjusted.

The` stopping of the `hydraulic impulses and consequently of the intermittent feed of the table T is obtained by pushing a piston 52 which carries a slope acting on -a rod 51. This rod pushes a check-valve 49 and opens a passage through which escapes freely the liquid displaced by the piston 4. After the withdrawal of the slope of the piston 52,1 a spring 50 brings the check-valve 49 back in its closing position.

The operation is as follows:

When the receiving piston 22 is lifted by the oil under pressure coming from the transmitter group, it causes the pinion 33 to turn. The piston 53, in engagement with the pinion moves therefore in the opposite direction.

At the end of the working stroke of the receiving piston 22, `the piston 53 has entered in the cylinder 54. The oil contained 4in the latter escapes by the passage 56, the

cross-section of which decreases gradually, thereby creat-` ing a back-pressure which is increasingly greater up to complete closure, which corresponds to the end of the working stroke of the piston 22. This back-pressure gradually opposes the movement of the receiving members and ensures a stopping without shock.

It is the piston 53 which, during the return stroke of the piston` 22, comes in contact with the adjustable stop; this contact takes place under a limited pressure since it is only subjected to the action of the return spring 24.

What I claim is:

l. In ahydraulic control device for imparting an intermittent displacement to a movable member, a casing, at least one cylinder in said casing, a working fluid in said casing and in said cylinder, means for compressing said fluid in said cylinder, said means comprising a piston in said cylinder, and means for displacing said piston in said cylinder, independent means for returning said piston to its initial position, a second cylinder` externally of said casing, a second piston in said second cylinder, fluidconveying means connecting the first cylinder to the second cylinder, a rack connected to said second piston, a pinion meshing with said rack, said pinion being related mechanically to the movable member to be displaced by means of a connection comprising a free wheel and a threaded member, and a motion-reversing device, means defining an exhaust outlet from said first-named cylinder and means defining a passageway connecting said firstnamed cylinder with said exhaust outlet, a third cylinder in said casing, a differential piston in said third cylinder, a closure device normally closing said passageway whereby an excess pressure is created in said first-named cylinder upon displacement of said first-named piston in said firstnamed cylinder under the influence of said displacing means, said closure device being displaceable to open said passageway, said third cylinder communicating with said fluid conveying means whereby said excess pressure acts upon said differential piston to move said differential piston into contact with said closure device to displace the latter in a direction to open said passageway, means for retracting said differential piston away from said closure device, and means acting upon said closure device to close said passageway, and valved means for supplying fluid to said first-named cylinder.

2. A hydraulic `control device as claimed in claim l, in which the independent means for returning the said first piston to its 4initial position comprise a spring.

3. A hydraulic control device as claimed in claim l, comprising a stop which is adjustably adapted to limit the stroke of the second piston.

4. A hydraulic control device as claimed in claim l, in which the fluid-conveying means connecting the two cylinders aforesaid includes a flexible pipe.

5. In a hydraulic control device for imparting an intermittent displacement to a movable member, a casing, means defining atleast one chamber in said casing, a working fluid in said casing and in said chamber, means for compressing said fluid in said chamber, said means comprising a piston in said chamber, and means for displacing said piston in said chamber, independent means for returning said piston to its initial position, means dening a second chamber externally of said casing, a seci ond piston in said second chamber, fluid-conveying means connecting the first chamber to the second chamber, means mechanically connecting said second piston with Vsaid movable member to be displaced to transmit the movements of said piston to said member, said mechanically connecting means including a one way drive, and a motion-reversing device, means defining an exhaust outlet from said first-named chamber and means defining a passageway connecting said first-named chamber with said exhaust outlet, means defining a third chamber in said casing, a differential piston in `said third chamber, a closure device normally closing said passageway whereby an excess pressure is created in said first-named chamber upon displacement of said first-named piston in said firstnamed chamber, said lclosure device being displaceable to open said passageway, said third chamber communicating with said fluid conveying means whereby said excess pressure acts upon said differential piston to move said differential piston into contact with said closure device to displace the latter in a direction to open said passageway, means for retracting said differential piston away from said closure device, and means acting upon said closure device to close said passageway, and valved means for supplying fluid to saidiirst-named chamber.

References Cited in the tile of this patent UNITED STATES PATENTS 661,448 Genty NOV. 6, 1900 1,273,6l8 lullen et al. July 23, 1918 1,983,884 Hele-Shaw et al Dec. ll, 1934 2,008,535 Winkler July 16, 1935 2,246,461 Cannon Illne 17, 1941 2,440,060 Page Apr. 20, 1948 2,486,244 Balsiger et al Oct. 25, 1949 

